Human beings, with proper training, are capable of swimming on the surface of the water. For brief periods, and with proper equipment for extended periods, swimmers can also swim under the surface of the water. People have long recognized, however, that the human anatomy is not designed to facilitate rapid and easy movement through the water. Most aquatic animals can swim much better and faster than the speediest human being.
In an effort to improve man's swimming abilities, a number of inventors have designed and produced fins adapted to be worn on the feet while swimming. Generally, fins have a foot retaining portion and a relatively large blade extending in a forward direction with respect to the body. Most are made from elastomeric materials such as rubber, polyurethane or silicones. Newer fins are made from combinations of these materials and may be reinforced with strengthening fillers such as graphite.
Some fins were designed to emulate the anatomy of aquatic animals. An example is U.S. Pat. No. 2,423,571 granted to Wilen in 1947. Wilen's designs are graceful and fluted and the inventor specifically states that he intended to copy the design of fish tails. Other fins were designed to take advantage hydrodynamic principles One example is U.S. Pat. No. 4,209,866 ranted to Loeffler in 1980. Loeffler presents a fin with a pivotally mounted blade which increases swimming efficiency. Another example is U.S. Pat. No. 3,183,529 granted to Beuchat in 1965. This design has a series of slots in the blade which jet water in the direction of swimming when the swimmer executes his downstroke. This is claimed to increase swimming speed.
Still others are designed to take advantage of the properties of newly available materials. U.S. Pat. Nos. 4,929,206 and 4,857,024 describe fins with upwardly curving blade tips. This design results in an opening of the blade as the swimmer executes a power or downstroke and a snapping action of the tips as the swimmer executes an upstroke. The opening action on the downstroke increases propelling force while the snapping action on the upstroke decreases the amount of energy needed by the swimmer to reposition his leg for another downstroke.
Much of the prior art equates power, resistance and propulsion. However, resistance is opposition of the water to the motion of the fin. The higher the resistance the harder the swimmer must work. Propulsion is the process of causing a body to move by exerting a force against it. In swim fins this can be equated to movement of the water over, under and through the blade. Power is force that moves the fin. It can only be provided by the swimmer's leg muscles.
To date, however, it has been the objective of all fin designers to design and produce fins that increase the swimmer's speed. They have attempted to do this by designing fins that increase propulsion. Among the designs that have been produced are fins having ribs (U.S. Pat. No. 4,820,218), flexible canals (U.S. Pat. No. 4,738,645), baffles (U.S. Pat. No. 4,627,820), stabilizers (U.S. Pat. No. 3,913,158), leading edges (U.S. Pat. No. 3,810,269), upcurving wingtips (U.S. Pat. No. 4,929,206 and 4,857,024), and hydrofoils (U.S. Pat. No. 4,944,703).
Battens provide either more or less resistance, however the surface area of the fin and thus the effective propulsion is not changed. Ribs are fixed and cannot be varied according to the needs of the swimmer and water conditions.
Baffles and vents combine forces exerted by the swimmer with water pressure forces moving through the blade. Such openings will not allow sufficient flow of water thus creating a backpressure which increases resistance. Stabilizers and leading edges are fixed and stationary, and will not respond to changes in water pressure or forces exerted by the swimmer.
As far as is known, no one has tried to design a fin for any other purpose. There are no fins designed to be made more resistive or more propulsive or both, depending on the swimmer's needs. There are no fins designed to help in rehabilitating physically handicapped people. There are no fins designed to compensate for disparities between one side of the swimmer's body and the other side. There are no fins designed to enable swimmers to achieve adequate exercise levels in a small pool. There are no fins designed to warm up muscles in preparation for competition. Development of a swim fin which could fulfill all of these requirements would represent a great improvement in the field of swim fin design and would satisfy a long felt need of the swimming public, disabled persons, divers, snorkelers and competition swimmers.